windows 8 does not recognise Macintosh HD, No drive Letter

Yosemite logical volumes cannot be read on Windows bootcamp anymore since they are not HFS+ volumes but they are now CoreStorage. Till Bootcamp is updated with drivers to allow read access to CoreStorage HFS+, you have lost functionality by upgrading to Yosemite. 😟.

You can verify this on the OS X side by running diskutil cs list in OS X terminal. If it returns any output, Windows cannot read such volumes.

it works fine on my windows 8.1 install after yosimite mac hd is still drive e and I can still read it

is hfs+ worth it over hfs ?

Can you run diskutil cs list on the OS X side?

There are some advantages of Core Storage, where a new physical disk can be added, removed, it has the ability to store files used at higher frequency on the the 'first' volume (which is meant to be an SSD). It is Apple's answer to Unix LVM and some additional features.

Confirmed. After installing 10.10, standard unencrypted HFS+ volumes are converted to CoreStorage LV's just like when enabling FileVault 2 except that the Logical Volume Family isn't flagged with encryption enabled. Since a CoreStorage LV is a variation of a file system (it's a logical volume manager) it has it's own on disk format. So until there's a Windows driver, it can't be read from Windows.

For any Linux users out there, note that you can't read this format either. Basically it's like we have a new file system and nothing outside of OS X can currently read it.

I was hoping that the Linux LVM folks would be able to accommodate the CS volumes, and they may in the future, like Ubuntu supports HFS+.

man diskutil

Spacebar to scroll down until you get to the CoreStorage section and then read. It's a chunk, but basically Core Storage is a logical volume manager, except unlike LVM/LVM2 on linux, this is apparently not open source. I'm not finding anything about it in Darwin/xnu. There's simply no way to by pass this, it's basically a file system on a file system (not technically correct but metaphorically correct), so the underlying "filesystem" or the metadata on each physical volume must be understood by some code to know how to assemble the PV's into LVG's and then LV's in order to even see the HFS+ volume to mount.

There appears to be a command 'diskutil cs revert' which should convert it from Core Storage back to a plain partition with HFS+ on it. I haven't tested this. There shouldn't be a negative consequence of it, but definitely have backups first. At this point the installer does not give us a choice, it will convert a plain partition HFS+ (non encrypted with FileVault 2) to a Core Storage volume which thus far isn't readable on Windows.

Hmm I'm not following the exact steps you took to avoid the convertion. I had a single partition OS X 10.9.5 installation (which of course has 3 partitions on disk), upgraded to 10.10 via the App Store, nothing special at all. And in the course of that upgrade, the HFS+ volume was converted to a Core Storage volume. I had no say in the matter, and no way to prevent it.

HFS (Mac OS Standard) and HFS+ (Mac OS Extended) are support by the linux kernel natively for read/write. HFSJ/HFSX (case-insensitive and case-sensivie, journaled) are supported by the linux kernel natively for read only. Near as I can tell there's simply no documentation on Core Storage anywhere, and I've been digging around very lightly in Darwin/xnu and can't find anything related to Core Storage there either, unlike HFS/HFS+. So I don't see how we get support for Core Storage in the linux kernel without a GPL2 compatible licensing of Core Storage. Someone could reverse engineer it and offer it out of tree of course, but that's trouble of its own.

I have also tried looking for something on the Developer links, but there is nothing substantial.